Microsoft bought Skype some time ago (link). The tech sites saw mainly two things as the reason:
- Deep Integration into Windows Phone 7 as the killer selling point for WP7
- Converting the Skype userbase to using MS products
I think the reason MS bought Skype could be targeting the enterprise markets. One of the first decisions made after the deal was official was to shut down the Asterisk connection plugin developed by Digium. While also the linked article states that it is unknown whether Microsoft actually had something to do with this, let’s at least consider it did:
The Skype integration into Asterisk was especially important for businesses, who wanted to keep Skype out of their infrastructure. Implementing Asterisk allowed communication with the Skype userbase through a safe and trusted channel. This is now cut and within the 2 year period Asterisk will continue working, they need to switch to another architecture. Enter “Microsoft Telephony and VoIP server” (not an actual product). For most enterprises a Microsoft proprietary application tunneling Skype would be the easiest upgrade path. MS would sell a few Windows Server licenses, the Telephony Server license and maybe some support. While I also see the two points mentioned above as the most important ones, the enterprise sector shouldn’t be underestimated, especially seeing that neither Google, Microsoft and especially Facebook do not have much enterprise penetration with their current VoIP and Videochat products, while Skype has that (at least at my work).